how do you calculate hydraulic hammer downstream of a control valve. Perrys section 6-44 talks about valve closure time to prevent surge but what about valve opening time to prevent surge on a downstream elbow. You could use F=ma but what would your mass be, would it be the entire mass of the fluid all the way to the point of a pressure generating device (ie a pump or pressurized gas blanket)? Would the valve opening time be an iterative calculation with the first slug of liquid being calculated using F=ma and subsequent calculations be made using pulsation calculations for an already packed line? My guess would be that the worse surge would be the initian F=ma surge and once the line was packed there would be no concern for hydraulic surge. I am also thinking about just putting in a small bypass to liquid pack the line before the main valve is open but still would like to back it up with calcs.